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Malaria Rise in Africa Parallels Warming Trends;
New Analysis Challenges Results of Previous Research
Researchers from the Johns Hopkins Bloomberg School of Public Health, the Earth Institute at Columbia University, the Tyndall Centre for Climate Change Research at the University of East Anglia, and other institutions conclude that the increase in the incidence of malaria in East Africa parallels warming trends over the last several decades. The new findings challenge the results of a study, "Climate change and resurgence of malaria in the East African highlands," which was previously published in the journal Nature. The original study, conducted by Simon Hay of the University of Oxford and his colleagues, found "no significant changes" in long-term climate. The new analysis, as well as its rebuttal, is published in the December 12, 2002 edition of Nature.
The Earth Institute's Cynthia Rosenzweig and her group at GISS at Columbia provided climate analysis and interpretation for the rebuttal. "Weather data is particularly sparse in East Africa, and the climate database used was originally created to pool information for analysis over large geographic areas. There is potential, therefore, for reaching spurious conclusions when using such climate data to study diseases at the local level," said Jonathan Patz, MD, MPH, lead author of the new analysis and assistant professor of environmental health sciences at Johns Hopkins.
Patz added that "Malaria is one of the world's most climate-sensitive diseases, and the African Highlands is an area of key importance for climate/malaria risk studies."
According to Dr. Patz and his colleagues, the previous study interpolated climate values to study locations at diverse elevations, differing on average by 575m, or approximating a 3¡C temperature deviation. Dr. Patz and colleagues argue that this approach crucially ignores temperature variability, particularly essential within an area of such large altitudinal contrasts.
"The climate dataset used is not designed to reveal climate trends for specific locations. It's appropriate for up-scaling information to African regions, not down-scaling to small area locations. It cannot support the type of analysis performed by Hay and his colleagues," explained Mike Hulme, PhD, co-author of the new analysis and executive director of the Tyndall Centre for Climate Change Research, School of Environmental Sciences, at the University of Anglia in Norwich, UK.
The new analysis found a mean warming trend of 0.15 degrees Celsius per decade from 1970 to 1998 across the same East African region included in Hay's study.
"Reliable assessment of the long-term malaria/climate relationship requires better local monitoring of appropriate climate and disease variables to attain databases that can support long-term trend analysis. Moreover, processes as diverse as climate and human disease require researchers from different fields to work together in order to best assess health implications of long term past climate trends or future climate change," said Dr. Patz.
"Regional Warming and Malaria Resurgence" was written by Jonathan A. Patz, Mike Hulme, Cynthia Rosenzweig, Timothy D. Mitchell, Richard A. Goldberg, Andrew K. Githeko, Subhash Lele, Anthony J. McMichael, and David Le Sueur. It is published in the December 12, 2002, edition of Nature.
"Climate Change and the Resurgence of Malaria in the East African Highlands" was written by Hay SI, Cox J, Rogers DJ, Randolph SE, Stern DI, Shanks GD, Myers MF, and Snow RW. It was published in the February 21, 2002, edition of Nature.
The Earth Institute at Columbia University is among the world’s leading academic centers for the integrated study of Earth, its environment, and society. The Earth Institute builds upon excellence in the core disciplines—earth sciences, biological sciences, engineering sciences, social sciences and health sciences—and stresses cross-disciplinary approaches to complex problems. Through its research, training and global partnerships, it mobilizes science and technology to advance sustainable development, while placing special emphasis on the needs of the world’s poor.